The relevant property is the closure of the set of rational numbers under the operation of addition.
Any rational number will do that.
Any rational number does.
Any rational number does.
Every rational number does.
Any other rational number.
Any other rational number.
Since the set of rational numbers is closed under addition, any rational number added to 0.5 will total another rational number.
Any and every rational number.
Any other rational number.
Any other rational number.
If an irrational number is added to, (or multiplied by) a rational number, the result will always be an irrational number.
Any other rational number.